1. Field of the Invention
The present invention relates first of all to a disk milling cutter for the milling of a crankshaft journal, including the two oil collar cheeks associated with it, and of recesses that act as oil grooves between the oil collar cheeks, with plate-shaped cutting inserts on its milling cutter periphery in the peripheral direction on its left and right sides.
2. Background Information
Using such disk milling cutters, crankshaft journals are machined as the workpiece is driven synchronously so that it rotates around its axis, together with both associated oil collar cheeks and together with the recesses in between that act as oil grooves, flank the cylindrical journal surface on both sides and maintain an appropriate distance from the oil collar cheeks. This milling is appropriately done using a single feed motion of the disk milling cutter, i.e. in one single operating process. The disk milling cutter is equipped or studded on its periphery in the peripheral direction, alternately on the left and right sides, with plate-shaped cutting inserts. On the disk milling cutter claimed by the present invention, the cutting inserts with their cover surfaces that contain the faces or chip faces are oriented essentially radially with respect to the axis of the milling cutter.
Crankshaft journals generally have only a limited diameter. The curvature of the surface of the crankshaft journals to be formed by the milling cutter into a cylindrical jacket is correspondingly severe. Consequently, on conventional disk milling cutters for this application only one milling cutter cutting edge is engaged at a time. This engagement occurs alternately on the left and on the right sides of the periphery of the disk milling cutter. This type of operation causes rough operation, which in turn results in the risk of an adverse effect on the surface quality.
The initial object of the present invention is therefore to improve the smoothness of operation of the disk milling cutter and thus to optimize the result of the milling operation.
The present invention teaches that the cutting inserts can be located on the periphery of the milling cutter with such close spacing, or narrow or tight pitch, that the length of the arc of contact between the beginning of the cut and the end of the cut of a cutting insert on the crankshaft journal is greater than one-half the spacing of the arrangement of the cutting inserts on the periphery of the milling cutter. In this context, one whole space, pitch, or spacing can be defined, either on the left side or on the right side of the periphery of the milling cutter, as the distance between two sequential cutting inserts in the peripheral direction of the milling cutter. The present invention consequently can make possible such a close spacing that the length of the arc of contact of the milling cutter is greater than one-half the milling cutter spacing on its right or on its left side. The length of the arc of contact is defined as the arc that is traveled by each milling cutter cutting edge between the beginning of the cut and the end of the cut on the crankshaft journal. Because the cutting inserts that are located on the left and right sides on the periphery of the milling cutter can be offset from each other by one-half space, which means that the left cutting inserts are in the centers of the spaces between the cutting inserts that are located on the right side (and vice versa), one-half of the space equals the peripheral arc of the milling cutter between a cutting edge on the left side and a neighboring cutting edge on the right.
The present invention teaches that more than just one cutting edge can essentially always be in contact with the workpiece. Thus there can be a cutting force load that is always pulsating between a bottom value and a top value. There are essentially no loads that alternate between zero and maximum. This feature is also an advantage in terms of machine dynamics and promotes a longer useful life of the equipment.
In at least one possible embodiment according to the present invention, the cutting force load can be kept substantially constant by the precise spacing of the cutting inserts. The precise spacing, as discussed above, can permit more than one cutting insert to be in contact with the workpiece, i.e. the crankshaft, in order to achieve a substantially smooth operation of the disk milling cutter. The smooth operation can essentially avoid the undulations or vibrations caused by the application of uneven cutting force loads. In at least one possible embodiment, the inserts can be spaced so that, during operation of the disk milling cutter, the preceding cutting insert, in the direction of rotation of the milling cutter, will disengage from the crankshaft while the following cutting insert, which is preferably located on the opposite side of the periphery of the milling cutter, begins engaging the crankshaft. Further, the degree of force applied by the preceding cutting insert can begin to decrease during disengagement, while the degree of force applied by the following cutting insert can begin to increase during disengagement at a rate and amount preferably substantially equivalent to the rate and amount of decrease of the force during disengagement of the preceding cutting insert. This balance between decreasing and increasing cutting force loads can provide for a substantially smooth operation of the milling cutter by substantially eliminating unbalanced force loads that can cause vibrations or undulations in the milling process.
In at least one further possible embodiment according to the present invention, the cutting inserts may not alternate from side to side about the periphery and may all be substantially similar in position.
In at least one other possible embodiment according to the present invention, the diameter of the workpiece to be machined, the diameter of the disk milling cutter, the spacing of the cutting inserts, and the depth at which the inserts are to cut into the workpiece all must be precisely calculated and measured for substantially optimal performance during the milling process. Each one of these measurements affects each one of the other measurements. If, for example, the cutting inserts were spaced improperly with relationship to the workpiece, unbalanced cutting force loads could occur. If the spacing were too small, the cutting force applied by the multiple inserts contacting the workpiece could cause an improper cut. If the spacing were too large, only one insert may contact the workpiece at any given time, which could also result in variations in the cutting force load from none to maximum, and thereby cause rough or imprecise cuts.
The disk milling cutter as described by the present invention takes advantage of the low wear on the peripheral length of the disk milling cutter by each individual cutting insert. This low wear on the peripheral length is made possible by the exclusive use of plate-shaped cutting inserts, which with their cover faces form a face or chip face and therebyxe2x80x94with reference to their plate-shaped configurationxe2x80x94can be oriented essentially radially on the periphery of the milling cutter. In one embodiment, the present invention teaches a disk milling cutter of a type in which the milling cutter can be equipped both on the left side and on the right side of its periphery with identically configured cutting inserts, which alsoxe2x80x94regardless of whether it is used on the left side or on the right side of the periphery of the milling cutterxe2x80x94are realized in the form of indexable cutting inserts, which make available cutting edges that can be placed in more than one cutting position. The cost advantages of using such indexable cutting inserts are generally known. In this document, when the term xe2x80x9cindexable insertxe2x80x9d is used, it should be understood in the sense of a xe2x80x9cdouble indexable insertxe2x80x9d because the indexing capability makes it possible to use the same insert on the left side and also on the right side of the milling cutter, and the other rotation is available for an additional cut on the left or on the right side. The term xe2x80x9ccutting edgexe2x80x9d as used here relates to a complete reproducing or matching, namely a combined or otherwise dual-function diameter and recessing cutting edge, which either on the left or on the right side of the crankshaft journal creates the complete final shape with a single feed motion. All these capabilities are made possible in a disk milling cutter according to at least one embodiment of the present invention, wherein each of the cutting inserts is an indexable insert with at least two cutting edges on the same side of the milling cutter that can be brought into the cutting position one after the other, and wherein each cutting insert is shaped and indexable so that it can be used on the same disk milling cutter both on its left side as well as on its right side.
The above discussed embodiments of the present invention will be described further hereinbelow with reference to the accompanying figures. When the word xe2x80x9cinventionxe2x80x9d is used in this specification, the word xe2x80x9cinventionxe2x80x9d includes xe2x80x9cinventionsxe2x80x9d, that is, the plural of xe2x80x9cinventionxe2x80x9d. By stating xe2x80x9cinventionxe2x80x9d, the Applicants do not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicants hereby assert that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.